In integrated circuit (such as microprocessor) fabrication process, a substrate, typically a silicon based wafer, goes through a number of processing steps in order to manufacture completed integrated circuits. Some of these steps include, but are not limited to, oxidation, circuit patterning, chemical etching, and metal deposition. One process, photolithography, is often used to transfer the pattern representing the circuit components onto the surface of the substrate.
In the photolithography process, a photo resist material is often deposited on the surface of the substrate. A mask is then placed over the substrate, often in the form of a patterned reticle or other pattern medium. An exposing source, such as light, passes through the pattern mask and exposes certain portions of the photo resist to create a particular desired circuit pattern. The exposed portion is then removed from the substrate using a developer solution.
The developer solution is typically dispensed across the surface of the substrate and allowed to briefly stand on the substrate in order to remove the exposed photo resist. The developer solution and the exposed photo resist are then removed from the substrate with a rinse solution, such as de-ionized water. Once completed, the substrate is ready for the next step in the process, which may be, for example, the etching process.
One technique often used to dispense and remove developer and the rinse solution is to slowly rotate the substrate and dispense, via a nozzle, the developer solution on the center of the substrate. The fluid may then radially distributes across the surface of the substrate. Once the developer has completed its reaction time with the exposed photo resist, the substrate is spun at a much higher revolutions per minute RPM such that the developer and exposed photo resist are spun off the substrate. The de-ionized water solution is then similarly dispensed and spun off to insure the exposed photo resist and developer are removed from the surface of the substrate.
A significant problem exists with dispensing the developer and rinse solution onto the substrate using the current dispensing nozzles. Due to the relatively low viscosity and low surface tension of the developer and even lower viscosity and surface tension of the rinse solution, a drip from the nozzle will often occur after the developer or the rinse solution has been stopped and before an arm carrying the nozzle is able to move the nozzle away from the substrate. Because of the delicate and unprotected state of the integrated circuits, drips on the substrate are very undesirable. Drips may cause fatal defects in the patterning of the integrated circuit directly hit by the drip as well as those in close proximity.